Dear Colleague,

A bug has been found in the Lattice Boltzmann Equation (LBE) code of DL_MESO 
2.5.

Lattice nodes that apply the Zou/He boundary condition for constant fluid 
velocities or densities should be included in the collision step along with all 
fluid nodes, excluding blank sites and bounce-back boundary nodes. In addition, 
all nodes containing fluid and boundaries in solute and temperature lattices 
(apart from blank nodes) should be collided. Unfortunately, until now the LBE 
code in DL_MESO has only applied collisions to lattice nodes with fluids and has 
excluded all boundary nodes. (Many thanks are due to Ernesto Monaco from the 
Technical University of Clausthal for bringing this bug to our attention.)

The fix for this bug cannot be implemented by simple changes to the code, since 
different conditions are required for the fluid, solute and temperature lattices 
during the collision step. Substantial changes have been made to the collision 
routines in the lbpSUB.cpp module to satisfy these conditions, including 
separating out fluid, solute and thermal collisions.

We therefore strongly recommend that all registered users download DL_MESO again 
using the instructions they received on registration to obtain the corrected 
version of the software. The decryption password has not changed and thus re-
registration is not required. The new and revised collision routines are listed 
in the revised version of the user manual. The LBE test cases involving Zou/He 
boundary conditions have also been recalculated: the results of these can be 
found in the DEMO/LBE directory of the package and in the Example Simulations 
page of the DL_MESO website (www.ccp5.ac.uk/DL_MESO).

Michael Seaton
2012-09-06